tcp: mitigate ACK loops for connections as tcp_request_sock
In the SYN_RECV state, where the TCP connection is represented by tcp_request_sock, we now rate-limit SYNACKs in response to a client's retransmitted SYNs: we do not send a SYNACK in response to client SYN if it has been less than sysctl_tcp_invalid_ratelimit (default 500ms) since we last sent a SYNACK in response to a client's retransmitted SYN. This allows the vast majority of legitimate client connections to proceed unimpeded, even for the most aggressive platforms, iOS and MacOS, which actually retransmit SYNs 1-second intervals for several times in a row. They use SYN RTO timeouts following the progression: 1,1,1,1,1,2,4,8,16,32. Reported-by: Avery Fay <avery@mixpanel.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Родитель
032ee42369
Коммит
a9b2c06dbe
|
@ -115,6 +115,7 @@ struct tcp_request_sock {
|
|||
u32 rcv_isn;
|
||||
u32 snt_isn;
|
||||
u32 snt_synack; /* synack sent time */
|
||||
u32 last_oow_ack_time; /* last SYNACK */
|
||||
u32 rcv_nxt; /* the ack # by SYNACK. For
|
||||
* FastOpen it's the seq#
|
||||
* after data-in-SYN.
|
||||
|
|
|
@ -1145,6 +1145,7 @@ static inline void tcp_openreq_init(struct request_sock *req,
|
|||
tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
|
||||
tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
|
||||
tcp_rsk(req)->snt_synack = tcp_time_stamp;
|
||||
tcp_rsk(req)->last_oow_ack_time = 0;
|
||||
req->mss = rx_opt->mss_clamp;
|
||||
req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
|
||||
ireq->tstamp_ok = rx_opt->tstamp_ok;
|
||||
|
|
|
@ -605,7 +605,11 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
|
|||
* Reset timer after retransmitting SYNACK, similar to
|
||||
* the idea of fast retransmit in recovery.
|
||||
*/
|
||||
if (!inet_rtx_syn_ack(sk, req))
|
||||
if (!tcp_oow_rate_limited(sock_net(sk), skb,
|
||||
LINUX_MIB_TCPACKSKIPPEDSYNRECV,
|
||||
&tcp_rsk(req)->last_oow_ack_time) &&
|
||||
|
||||
!inet_rtx_syn_ack(sk, req))
|
||||
req->expires = min(TCP_TIMEOUT_INIT << req->num_timeout,
|
||||
TCP_RTO_MAX) + jiffies;
|
||||
return NULL;
|
||||
|
|
Загрузка…
Ссылка в новой задаче